Method for introducing boric acid into liquid hydrocarbons during their air oxidation to the corresponding alcohols

ABSTRACT

A METHOD FOR IMPROVING THE AIR OXIDATION OF HYDROCARBONS TO THEIR CORRESPONDING ALCOHOLS BY ADDING DRIED BORIC ACID TO LIQUID HYDROCARBON IN AN AIR OXIDATION REACTOR BY DELIVERING THE BORIC ACID FROM A COLLECTING CONTAINER TO AN INTERMEDIATE CONTAINER AND FROM THERE THROUGH A POCKET WHEEL TO BE CARRIED BY AN INERT GAS THROUGH A DIP TUBE IMMERSED IN THE HYDROCARBON.

Nov. 7, 1972 I H. GRASEMANN 3,702,319

' METHOD FOR INTRODUCING BORIC ACID INTO LIQUID HYDROGARBONS DURINGTHEIR AIR OXIDATION TO THE CORRESPONDING ALCOHOLS Filed Nov. 6, 1968!NVENTOR HORST GRASEMANN ATTORNEY United States Patent Office PatentedNov. 7, 1972 JVIETHOD FOR INTRODUCING BORIC ACID INTO LIQUIDHYDROCARBONS DURING THEIR AIR OXIDATION TO THE CORRESPONDING ALCOHOLSHorst Grasemann, Marl, Germany, assignor to Chemische Werke Huels, A.G.,Marl, Germany Filed Nov. 6, 1968, Ser. No. 773,717 Claims priority,application Germany, Nov. 10, 1967, P 16 43 825.8 Int. Cl. C07c 35/02US. Cl. 260-617 H 15 Claims ABSTRACT OF THE DISCLOSURE A method forimproving the air oxidation of hydrocarbons to their correspondingalcohols by adding dried boric acid to liquid hydrocarbon in an airoxidation reactor by delivering the boric acid from a collectingcontainer to an intermediate container and from there through a pocketwheel to be carried by an inert gas through a dip tube immersed in thehydrocarbon.

CROSS-REFERENCE TO RELATED APPLICATIONS Applicant claims priority under35 U.S.C. 119 for application Ser. No. 43,804 IVb/ 12 o filed in thePatent Oflice of the Federal Republic of Germany on Nov. 10, 1967.

BACKGROUND OF THE INVENTION The field of the invention is air oxidationof hydrocarbons to their corresponding alcohols.

The state of the prior art is set forth in British Pat. 1,069,733;French Pat. 1,445,874; and US. Pat. 3,287,423 of Steeman et a1.

Steeman et al. disclose the improvement of the process of preparingcyclic alcohols by the air oxidation of hydrocarbons, having asuspension of boric acidv therein, by mixing the hydrocarbons with anaqueous solution of boric acid and then evaporating all the water fromthe mixture to leave behind a suspension of solid boric acid inhydrocarbons.

In the method disclosed in British Pat. 1,069,733, the boric acidsolution resulting from the hydrolysis of boric acid ester is dehydratedin the presence of the hydrocarbon being oxidized. The process iscarried out in two stages with the aid of an azeotropic distillation.When carrying out the method according to the British patent, theimpurities dissolved in the water are not removed and are returned tothe oxidation step.

It is particularly difiicult to deliver dried boric acid into theoxidation chamber because the normal conveyor means like pumps or twinscrew conveyers are subjected to considerable wear due to the hardnessof the dried boric acid.

It is not possible to employ a hydrocarbon such as cyclododecane forconveying the dried boric acid because of the high melting point ofcyclododecane. If the cyclododecane is warmed above the melting pointand boric acid is dissolved therein, then it is necessary to provide forthe control of the considerable vapor pressure which results.

Since a mixture of dried boric acid and liquid cyclododecane solidifiesto a hard mass which easily clogs the means of conducting, this factmust be taken into consideration. Considerable expense is required toclear conduits which are clogged with a hard mass of solidified boricacid and cyclododecane.

French Pat. 1,445,874 teaches the introduction of a boric acid watersolution, or preferably a water moist boric acid, into the hydrocarbonoxidation reactor by means of a dip tube immersed in the hydrocarbon.The process of oxidation is disturbed because of the water which isintroduced with the boric acid. When the boric acid is introduced intothe reactor through the dip tube by means of air pressure, a part of theboric acid is blown out of the reactor resulting in the clogging of theexhaust gas channels. The boric acid is blown out because of the amountof air and the pressure required to introduce the boric acid.Thereafter, the boric acid lost cannot provide the protectiveesterification needed and because of the entrained boric acid in the gaschamber of the reactor, the exhaust gas channels become clogged. The airused to introduce the boric acid precipitates the reaction in anuncontrolled manner.

It is not feasible to introduce the air carrier at the same time as theoxidation air because the oxidation air must be introduced into thereactor in a very fine distribution. Even if inert gases are employed inplace of the air carrier, the same disadvantages exist.

SUMMARY OF THE INVENTION It is therefore an object of the presentinvention to introduce dried boric acid into liquid hydrocarbon duringthe air oxidation to the corresponding alcohols by using a dip tubeimmersed in hydrocarbon.

According to the present invention the oxidation of the hydrocarbon inthe presence of boric acid is interrupted and the resulting boric acidester is saponified to yield a saturated boric acid solution inadmixture with the products of oxidation. The boric acid solution is separated from the product and the boric acid crystallizes from thesaturated boric acid solution. The boric acid is processed in the usualmanner, cleaned, dried and transported into a collecting container.

It has been found that the disadvantages of the prior art can be avoidedif the boric acid which is separated and dried from the hydrolysis stepof the boric acid ester, is first transported from the collectingcontainer to an intermediate container, and then from the intermediatecontainer is delivered by a known sluice installation and an inert gasunder pressure into a dip tube immersed in the hydrocarbon.

A pocket wheel has proved to be particularly advantageous as the sluiceinstallation.

BRIEF DESCRIPTION OF THE DRAWING The drawing appended hereto is adiagrammatic representation of the apparatus used in carrying out theprocess.

The improvement of the present invention is described by reference" tothe drawing. From a silo 1 the boric acid is'delivered over ametering-belt scale 2 and through an injector 3 to the cyclone 4. Theboric acid falls into the intermediate chamber 5. A pocket wheel 6delivers it to the dip tube 9 and into the reactor 8. A current ofnitrogen flows through conduit 7 into the dip tube 9. Conveyor air fromthe injector 3 escapes through the conduit 10. The dispersion of boricacid in hydrocarbon is agitated by stirrer 11 and air is introduced bynozzle 12.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hydrocarbons found particularlysuitable for use in the present oxidation process are saturatedaliphatic hydrocarbons containing at least 10 carbon atoms andcycloaliphatic hydrocarbons containing at least 6 carbon atoms, andmixtures thereof. That is to say, any nonaromatic hydrocarbon can beoxidized in liquid phase under the reaction conditions.

Examples of suitable cycloaliphatic hydrocarbons include cyclohexane,cycloheptane, cyclooctane, cyclononane, particularly cyclodecane,cycloundecane and cyclododecane. Also polycyclic cycloaliphatichydrocarbons, e.g. perhydronaphthalene and unsaturated cycloaliphatichydrocarbons, e.g. tetrahydronaphthalene can be used.

Aliphatic hydrocarbons can be, for example, decane, undecane, dodecane,tridecane and tetradecane. Also branched chain isomers of theprecedingly described saturated aliphatic hydrocarbons and alsounsaturated a1iphatic hydrocarbons can be used.

Because of the intermediate containers a sufiicient density of the boricacid anhydride is achieved on the side opposite to the entrance to thereactor.

' It is to be expected that hydrocarbon vapors such as cyclododecanevapors would form deposits with the boric acid to clog the sluiceinstallation, but because of the cooperation between the intermediatecontainer and the sluice installation, the boric acid is introduced intothe reactor without difficulty.

As the inert gas, nitrogen is delivered under excess pressure throughthe dip tube immersed in the hydrocarbon. The excess pressure isdependent upon the immersion depth of the tube and upon the throttlingof the exhaust gas path. The usual excess pressure of the inert gasamounts to about 0.1 to 0.2 atmospheres absolute.

This pressure is sufiicient to overcome the minor excess'pressurepresent in the reactor and therefore avoids the syphoning action ofcyclododecane in the dip tube.

The nitrogen is usually introduced in amounts of about 100-500 litresper hour.

The immersion tube is continuously rinsed with small amounts of inertgas through injector 7, and this rinsing continues during the fillingand draining of the hydrocarbon oxidation reactor.

Dried boric acid is advantageously removed from silo 1 under conditionsof fluidized air with the aid of an injector via a measuring device,such as a metering-belt scale into the intermediate container. Theintermediate container 5 is advantageously located above the hydrocarbonoxidation reactor 8.

By carrying out the process according to the present invention, it ispossible to remove all of the air used for fluidizing the product in thesilo.

The intermediate container is connected by a sluice installation to thedip tube immersed in the hydrocarbon. The sluice installation ispreferably a rotary vane feeder. A constant stream of nitrogen of about100-500 liters per hour is blown into the dip tube through conduit 7 andthis prevents cyclododecane vapors from rising into the path of thedescending dried boric acid.

The dried boric acid can be carried from the intermediate container tothe site of the oxidation reaction in a continuous or in a discontinuousmanner. As dried boric acid especially is used meta-boric acid. Alsoorthoboric acid may be used. Boric acid anhydride is less suitable forthe reaction.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The following preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the specification and claims in any Way whatsoever.

EXAMPLE 1 Comparative example An agitated vessel having a 20 cubic metercapacity is charged with 12,000 kilograms of cyclododecane feed in aboutone hour at 150-180 C. There are also charged to the reactor over a spanof about 4-5 hours 400 cubic meters per hour of air of which about 80%of the oxygen therein is consumed during the oxidation reaction. Inaddition, 100 kilograms per hour of meta-boric acid are continuouslypneumatically added by means of a dip tube immersed in the cyclododecaneto the oxidation mixture during the course of the reaction. After aconversion of 30%, the oxidation reaction is interrupted and theresulting boric acid ester is thereafter saponified at C. with 2200litres of water to yield a saturated boric acid solution in admixturewith the products of oxidation. After separating the boric acid solution(lower layer) from the product (upper layer), the latter product is thenpurified in a conventional manner by fractional distillation thereof.The yield of cyclododecanol/ one is 80.5

mole percent of theoretical based on the reacted hydrocarbon. During thereaction the dip tube is often clogged by the boric acid. Therefore thereaction must be interrupted and the dip tube must be cleaned.

EXAMPLE 2 (Demonstrating the invention) Example one is repeated. Inplace of the dip tube immersed in the cyclododecane, the apparatusaccording to the invention is used. A silo contains the dried meta-boricacid. The boric acid is transferred to an intermediate container, thenremoved from said intermediate container in incremental portions by apocket wheel and delivered said incremental portions of boric acid by aflow of an inert gas (nitrogen) under an excess pressure of 0.1 to 0.2atmospheres (about to 500 litres per hour) through said dip tubeimmersed in the cyclododecane. The yield of cyclododecanol/ one is 80.5mole percent of theoretical based on the reacted hydrocarbon. The diptube is not clogged by the boric acid, and the time to carry out thereaction is shorted. No cleaning step and no interruption of thereaction is necessary.

The preceding examples can be repeated with similar success bysubstituting the generically and specifically described reactants andoperating conditions of this invention for those used in the precedingexamples.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention, and withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

What is claimed is:

1. In the method of air oxidation of non-aromatic hydrocarbons to theircorresponding alcohols by introducing boric acid into an aerated liquidphase, non-aromatic hydrocarbon selected from the group consisting ofsaturated aliphatic hydrocarbons containing at least 10 carbon atoms andcycloaliphtaic hydrocarbons containing at least 6 carbon atoms, andmixtures thereof whereby hydrocarbyl esters of the boric acid areformed, saponifying the esters formed, separating and drying the boricacid and reintroducing said boric acid to the oxidation step, theimprovement comprising:

(a) introducing the dried boric acid into a collecting container; and

(b) delivering said boric acid under the force of gravity under anenveloping continuous flow of inert gas through a dip tube immersed insaid non-aromatic hydrocarbon located in an oxidation zone, said inertgas being maintained continuously at a positive pressure with respect tothe pressure of the reactor, whereby said non-aromatic hydrocarbon ishindered from passing up into the tube.

2. A method as defined by claim 1, further comprising the intermediatesteps of:

transferring the boric acid from the collecting container to anintermediate container, and removing the boric acid from theintermediate container in incremental portions.

3. A method as defined by claim 2 wherein said intermediate container isdisposed above the dip tube.

4. A method as defined by claim 1, further comprising introducing airthrough a nozzle immersed in said hydrocarbon in the same oxidation zonewherein said boric acid is fed through said dip tube.

5. A method as defined by claim 4, said dip tube being continuouslyrinsed by said inert gas during the filling and draining of theoxidation reactor.

6. The method of claim 1, wherein said hydrocarbon is cyclododecane.

7. The method of claim 3, wherein said incremental portions aredelivered by a rotary -vane feeder.

8. A method as defined by claim 7 wherein boric acid is fed through saidrotary vane feeder into the top of said dip tube and wherein inert gasis fed into said dip tube at a position downstream of said rotary vanefeeder.

9. The method of claim 1, wherein said inert gas is nitrogen.

10. In the method of air oxidation of non-aromatic hydrocarbons to theircorresponding alcohols by introducing boric acid into an aerated liquidphase, non-aromatic hydrocarbon selected from the group consisting ofsaturated aliphatic hydrocarbons containing at least 10 carbon atoms andcycloaliphatic hydrocarbons containing at least 6 carbon atoms, andmixtures thereof whereby hydrocarbon esters of the boric acid areformed, saponifying the esters formed, separating and drying the boricacid and introducing said boric acid to the oxidation step, theimprovement comprising:

(a) gravity feeding the dried boric acid into a dip tube immersed intosaid non-aromatic hydrocarbon located in an oxidation zone; and

(b) simultaneously and continuously passing an inert gas into said diptube to envelop said boric acid, said inert gas being continuouslymaintained at a positive pressure with respect to the reactor, wherebysaid nonaromatic hydrocarbon is prevented from passing up into the diptube.

11. The method of claim 10, wherein said hydrocarbon is cyclododecane.

12. The method of claim 10, wherein said inert gas is nitrogen.

13. The method of claim 10 wherein said inert gas is maintained at apositive pressure of about 0.1-0.2 atmospheres absolute with respect tothe reactor.

14. A method as defined by claim 13, inert gas being introduced intosaid dip tube at a position below the introduction of boric acid intothe dip tube.

15. A method as defined by claim 10, further comprising introducing airthrough a nozzle immersed in said hydrocarbon in the same oxidation zonewherein said boric acid is fed through said dip tube.

References Cited UNITED STATES PATENTS 2,133,311 1-0/ 1938 Shuman 232843,109,864 11/1963 Fox et al 260-617 3,336,390 8/1967 Nelsen et a1 260617FOREIGN PATENTS 1,445,874 6/19 66 France 260--617 1,110,396 4/1968 GreatBritain 260-617 BERNARD HELFIN, Primary Examiner M. W. GLYNN, AssistantExaminer US. Cl. X.R 260-686 B, 597 R, 617 F, 631 B, 639 -B; 23-260

